1. Field of the Invention
The present invention pertains generally to administering an aerosolized medicament to a patient, and more particularly, to optimizing the delivery of a respiratory maneuver to increase the effectiveness of medicament delivery.
2. Description of the Related Art
It is known to deliver a medicament via a patient's respiratory tract. Such a delivery approach has allowed the development of therapeutic regimens for treating localized and systemic effects of diseases, especially diseases affecting the pulmonary system.
A nebulizer is a common device employed to deliver medicaments via the respiratory tract. Generally, a nebulizer converts an aqueous-based medicament into an aerosol which is inhaled by a patient. Nebulizers may employ different mechanisms for aerosolizing a medicament. For example, pneumatic (or jet) nebulizers employ compressed air to disperse the aqueous-based medicament into aerosol form. An ultrasonic nebulizer, in contrast, employs an electrical source to excite a piezoelectric element which generates high frequency vibrations. These vibrations cause small droplets to separate from the surface of the aqueous-based medicament, thus forming an aerosol. Vibrating mesh technology (VMT) nebulizers employ a mesh having a number of microscopic apertures therein. A vibration is induced in the mesh (or in another component within the nebulizer) which causes the aqueous-based medicament to be extruded through the mesh apertures. The aqueous-based medicament is ejected from the mesh apertures in aerosol form.
It is important that the dosage of medicament prescribed by a physician be administered in a reproducible and precise manner. Reproducibility and precision are greatly dependent upon one or more respiration maneuvers performed during administration of the medicament. The terms “respiration maneuver”, “maneuver”, and derivatives thereof refer to a number of respiratory cycle characteristics and/or dosing characteristics related to the administration of a partial and/or complete dose of a medicament. The term respiration maneuver may be understood to encompass, for example and without limitation, the number of breathes per minute (BPM), the inspiratory flow rate, the tidal volume, the volume of aerosol delivered to the patient, the aerosol pulse duration, and the duration of the dosing event.
U.S. patent application Ser. No. 10/535,597 to Denyer et al., which has the same inventorship and assignee as the instant application, the entire contents of which are incorporated herein, teaches a respiration maneuver which improves the precision and repeatability of medicament delivery to a patient. Generally, Denyer et al. teach a method of generating signals in a drug delivery apparatus through which a patient is receiving a dose of medicament. These signals may be used as feedback to aid the patient in completing a desired respiration maneuver. Denyer et al., however, is generally directed to patients capable of spontaneous breathing (e.g., non-ventilated patients). Mechanically ventilated patients, in contrast, may not be able to adequately respond to the generated feedback signals, and thus fail to complete the desired respiratory maneuver.
The delivery of an aerosolized medicament to a patient through a ventilator circuit can be inefficient. In some cases, only ten to thirty percent of the nominal dose actually reaches the patient. The remaining medicament may be, for instance, carried away in the exhalation stream or lost to impaction with the ventilator circuit, endotracheal tube, and the patient's upper airway.
Attempts made to reduce medicament lost in the exhalation stream include, for example, triggering the aerosol generator only during inhalation, increasing the sedimentation time, and orienting the patient's position during administration of the aerosolized medicament. Attempts made to reduce medicament loss due to impaction include, for example, relocating the aerosol generator (e.g., a nebulizer) between the ventilator circuit and patient interface device (e.g., endotracheal tube; mask; etc.), suspending humidification during aerosol generation, and reducing the inhalation flow rate. Each of these attempts produce less than desirable results and generally requires an affirmative act by the clinician. For example, a clinician must manually adjust the ventilator's settings to reduce the inhalation flow rate.
Accordingly, a need exists for an apparatus and method for providing improved delivery of an aerosolized medicament to a ventilated patient which overcomes these and other problems associated with known systems.